Electric kiln



Oct. 3l, 1967 G, B. RANDALL ELECTRIC KILN 2 Sheets-Sheet l Filed sept. 12, 1966 f ff,

/N VEN T0@ GEORGE B. RANDALL By BHL/MAGMA Oct. 31, 1967 G. B. RANDALL ELECTRIC KILN 2 Sheets-Sheet 2 Filed sept. 12, 1966 /NVE/VTO/Q. GEORGE B, RANDALL 5y Gm GJV M United States Patent C 3,350,493 ELECTRIC KILN George B. Randall, Linder and La Grasse Sts., Waddington, N.Y. 13694 Filed Sept. 12, 1966, Ser. No. 578,559 7 Claims. (Cl. 13-22) This invention relates to electric kilns and more particularly to means for securing the heater elements in sidewall grooves of the kiln.

Conventionally the coils of the electric heater wires are contained in grooves which encircle the inner surface of the kiln chamber. When the coils become heated they expand and tend to elongate and work their way out of the grooves. After a coil is once heated the wire becomes brittle so that it is necessary to heat the coil again to restore its resiliency before it can be pushed, while hot, back in the groove, a process which most operators do not like.

The principal object of the invention is to provide means at the corners of the chamber, where the elements are particularly likely to creep out of the grooves, to secure the coils in the grooves.

Another important object is to provide the grooves with a cross-sectional configuration providing means for retaining the coils in the grooves.

Another object is to provide means at the corners of the kiln for interlocking the sidewall lining material firmly in place.

Still another object is to provide a kiln construction providing for the most economical use of the comparatively expensive iire brick kiln lining material.

Other objects and advantages will become apparent from the following description in conjunction with the appended drawings, in which FIGURE l is a perspective view of a kiln according to the invention;

FIGURE 2 is an enlarged fragmentary plan view thereof with cover removed;

FIGURE 3 is a sectional View on the line 3-3 0f FIGURE 2;

FIGURE 4 is an enlarged exploded plan view `of one of the corner post members shown in FIGURE 2, together with an associated retainer rod;

FIGURE 5 is an enlarged fragmentary sectional view on the line 5-5 of FIGURE 2;

FIGURE 6 is an enlarged fragmentary elevational view of a portion of one of the chamber walls;

FIGURE 7 is a view similar to FIGURE 2, of a modified kiln construction; and

FIGURE 8 is a similar view of another modified kiln construction.

Referring to FIGURE l, a kiln 1) is shown having a cover 11, a steel housing 12 to which is secured a tubular cover 13 housing the electrical connections to the coils, and an electric supply wire 14. In the housing or case 12, the lire brick lining 15 has grooves 16 opening into the article receiving chamber 17. These grooves contain electric resistance elements in the form of resistance wire spiral coils 18.

As best seen in FIGURE 3, the fire brick lining material 15 is held in place and spaced from the sheet steel housing by pads 19 of insulating material such as glass wool. The heating elements 18 lie in grooves 16 and extend completely around the chamber 17. A conventional manner of attaching the ends of each element to the supply wire 14 is indicated in FIGURE 6 in which one end of an element may be attached to a terminal in cover 13, led through a hole 21 in the sidewall, twice around the chamber passing from one groove 16 to the next at 22 and back out through a hole 23 to another terminal under cover 13.

Referring to FIGURE 2, the lining 15 comprises four rectangular sidewall units or slabs 15a, 15b, 15C and 15d (not shown), one at each side, and four corner posts 25, one at each corner. The corner posts 25 have vertically disposed ribs 26 along two adjacent sides, as best seen in FIGURE 4, and the ends of the units 15a-d are provided with mating grooves 27 so that the units and posts are locked together by the containing housing 12 and insulation 18.

Posts 25 are of such cross-sectional size that the units, when engaged therewith, have contiguous end edges which abut one another along a vertical line 28 at each corner. Units 15a and 15b meet along the line 28, for example, at this corner to form the corner of chamber 17.

Each lpost 25 has a curved, horizontally disposed groove 30 in registry with the grooves 16 of the units 15a-d so that the element coils 18 can pass therein around the corners. The corner between the ribbed sides of each post 25 is vertically slotted at 31, as shown, so that a porcelain rod 32 can be inserted from the top as indicated in broken lines in FIGURE 4.

Referring to FIGURE 6, each groove 16 in the sidewall units 15, and groove 30 in the posts 25, is generally elliptical in cross section with a narrower neck portion 33 opening into chamber 17. The neck 33 is just slightly narrower by a couple of thousandths of an inch than the diameter of the element coil 18 so that the coil can be forced into the groove after the units 15a-d and posts 25 have been secured within housing 16. The sidewall material is friable, somewhat like chalk, and the coils are resilient when new, so this is easily done.

Grooves 16 and 30 are routed or gouged out of the comparatively soft and chalk-like tire brick friable material of the sidewalls and posts to extend both above and below the neck 33 so that when the coils are heated and creep or expand horizontally there is room for expansion in the groove away from the neck.

In operation, after the posts and sidewall units have been assembled in housing 16, and coils 18 inserted in grooves 16, the ends of the coils are connected in their operative circuits in conventional manner. Rods 32 are then inserted downward in the slots 31 between the element coils 18 in grooves 30 and the abutting end edges of units 15a-d at 28 at each corner to prevent the coils from creepint7 out vof the grooves at the corners.

This construction also has the advantage of being economical of the sidewall material which comes in standard lengths. The sides of the chamber can be the length of each unit 15 and such units as are damaged may be used for forming the posts.

It will be noted also that sidewall units 15u41 and posts 25 may be shaped at the top with a shoulder 34 (FIGURE 2) to form an upstanding rib around the chamber 17 on which cover 11 may rest.

In FIGURE 7 a modified corner construction is shown in which posts are not used. The sidewall units 35 are notched or rabbeted, as shown, at the corners to form mitred ends. The units 35 are grooved as described above for element coils 18 to lie therein.

At each chamber corner, however, one unit 35 is notched out or grooved vertically at 36 from top to bottom so that a rod 32 can be inserted therein from the top between the abutting chamber surface edges and the element coils lying in the intersections of the grooves.

In FIGURE 8 another kiln construction is diagrammatically shown, the kiln chamber 4t) being polygonal in cross-section. The sidewall liner units 41 are mtred and rabbeted, as shown, at each corner. Each unit has grooves 16 thereacross as described above, the grooves 16 of one unit in registry with the grooves of the adjacent unit so that heating element coils 18 can be inserted in the grooves to extend completely around the chamber 40.

At each chamber corner surface edge 42, immediately outside the abutting edges, the end of each unit is notched or slotted vertically to form a reentrantly angled slot 43. When the units are assembled and elements 18 are inserted in grooves 16, porcelain rods 44, which are triangular in cross-section, are inserted down in the pairs of slots at each chamber corner between the abutting surface edges and the elements 18 in the grooves to retain the elements in the grooves.

What is claimed is:

1. In an electric kiln of the type having sidewalls of flat heat resisting fire brick units of friable material in end abutting relation about an article receiving chamber, the sidewalls having a series of horizontally disposed parallel inwardly exposed grooves around the chamber, the grooves of each unit intersecting the grooves of the adjacent unit at the chamber corners and having electric resistance elements therein passing around the chamber; a corner construction comprising: the abutting units being disposed so as to have abutting vertical inner surface edges between the grooves, at least one end abutting unit at the corner having a vertically disposed slot therein spaced outwardly of the abutting inner edges and extending down from the top of the unit through the groove intersections, and a rod of refractory material in the slot between the elements and the abutting inner edges for securing the elements in the grooves at the corner.

2. A rectangular electric kiln having each of its sidewalls around an article receiving chamber lined with a rectangular iire brick unit of friable material, the units being disposed with abutting end inner edges at the corners of the chamber, a rectangular tire brick post of friable material at each corner having adjacent sides abutting the adjacent edge of each unit at the corner, the units and posts having a series of horizontally disposed grooves formed therein, electrical resistance elements in the grooves extending around the sidewalls, the grooves being open to the chamber, each corner post having a vertically extending slot along the corner adjacent the abutting inner edges, and a rod of refractory material in each slot between the elements and the abutting inner edges to secure the elements in the grooves at the corners.

3. The kiln as delined in claim 2 characterized by the ends of the units and the adjacent sides of the abutting posts having cooperating vertically extending ridges and grooves for interlocking each post and adjacent units at the corners.

4. The kiln as defined in claim 2 characterized by the elements being wire coils, and the grooves having a comparatively narrow neck portion open to the chamber and a comparatively wider deeper portion extending above and below the neck portion, the neck portion being of a width substantially less than the diameter of the element coil.

5. A polygonal electric kiln having each of its sidewalls around an article receiving chamber lined With a rectangular re brick unit of friable material, the units being disposed with abutting mitred ends at the corners, and having end abutting inner surface vertical edges, the units having a series of horizontally disposed grooves formed therein, electrical resistance elements in the grooves passing around the sidewalls, the grooves being open to the chamber, the ends of the units having vertical slots therein immediately outward of the abutting inner edges, and a rod of refractory material at each corner in the slots between the abutting inner edges and the elements to secure the elements in the grooves at the corners.

6. The kiln as defined in claim 5 characterized by the abutting mitred ends of the units having cooperating vertically extending ridges and grooves for interlocking the abutting ends at the corners.

7. The kiln as defined in claim 5 characterized by the elements being wire coils, and the grooves having a comparatively narrow neck open to the chamber and a comparatively wider deeper portion extending above and below the neck portion, the neck portion being of a width substantially less than the dia-meter of the element coil.

References Cited UNITED STATES PATENTS 1,057,745 4/1913 Kohn 219-422 2,202,874 6/ 1940 Smalley 13-25 2,424,780 7/1947 Trent 174 138 2,744,946 5/ 1956 Lewicki 13-22 2,963,529 12/1960 Schmidt 13-22 2,978,563 4/1961 Hackman 219-375 FOREIGN PATENTS 505,200 9/1919 France. 591,285 4/ 1925 France.

RICHARD M. WOOD, Primary Examiner.

V. Y. MAYEWSKY, Assistant Examiner. 

1. IN AN ELECTRICAL KLIN OF THE TYPE HAVING SIDEWALLS OF FLAT HEAT RESISTING FIRE BRICK UNITS OF FRIABLE MATERIAL IN END ABUTTING RELATION ABOUT AN ARTICLE RECEIVING CHAMBER, THE SIDEWALLS HAVING A SERIES OF HORIZONTALLY DISPOSED PARALLEL INWARDLY EXPOSED GROOVES AROUND THE CHAMBER, THE GROOVES OF EACH UNIT INTERSECTING THE GROOVES OF THE ADJACENT UNIT AT THE CHAMBER CORNERS AND HAVING ELECTRIC RESISTANCE ELEMENTS THEREIN PASSING AROUND THE CHAMBER; A CORNER CONSTRUCTION COMPRISING: THE ABUTTING UNITS BEING DISPOSED SO AS TO HAVE ABUTTING VERTICAL INNER SURFACE EDGES BETWEEN THE GROOVES AT LEAST ONE END ABUTTING UNIT AT THE CORNER HAVING A VERTICALLY DISPOSED SLOT THEREIN SPACED OUTWARDLY OF THE ABUTTING INNER EDGES AND EXTENDING DOWN FROM THE TOP OF THE UNIT THROUGH THE GROOVE INTERSECTIONS, AND A ROD OF REFRACTORY MATERIAL IN THE SLOT BETWEEN THE ELEMENTS AND THE ABUTTING INNER EDGES FOR SECURING THE ELEMENTS IN THE GROOVES AT THE CORNER. 